The IACOB project - XII. New grid of northern standards for the spectral classification of B-type stars

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Table 3

Main standard stars and classification criteria for early-B stars.

	V	IV	III	II	Ib	Iab	Ia	Ia⁺
B0	τ Sco	HD 48434			HD 205196		ε Ori
		Si IV 4116/He I 4121 increases					Very strong Si IV 4089
	All He II lines present see main text for criteria against O-type	He II 4686 weaker compared to other He II or He I 4713			HD 164402	Very strong C III 4650 Weak He II 4686

B0.2	HD 2083	ϕ¹ Ori	HD 6675		HD 16808	69 Cyg	HD 171012
			As in B0				As in B0
	He II 4200 hardly seen or absent

B0.5	HD 36960		1 Cas	HD 193007	26 Cep		κ Ori
					HD 192422		HD 194839
	He II 4541 hardly seen or absent
	Si III 4553 comparable to Si IV 4089	increasing Si IV 4089/He I 4144 and Si III 4553/He I 4387

B0.7	HD 37042	ξ¹ CMa	HD 13969	HD 193076	HD 190066		HD 216411
	HD 201795				HD 14053
	He II 4686 barely noticeable	Si III 4553 somewhat stronger than Si IV 4089
	C III/ O II 4650 weaker compared to other O II	Si III 4553 somewhat stronger than Si IV 4089 Same luminosity criteria as in B0.5

B1	HD 24131, ω¹ Sco	β CMa (B1 II–III)			ζ Per	HD 13854		HD 169454

	He II 4686 not seen
	Si IV 4089 hardly seen, many O II lines	Si III 4553/ He I 4387, 4713 main luminosity criterion

B1.5	HD 35299, HD 215191		12 Lac	ε CMa	HD 13841	HD 5551	HD 14956	HD 190603
Si IV 4089 not seen
					HD 193183	Si II 4128 appears
	C II 4267 stronger than neighbour O II						Strong N II lines

Notes. Criteria in italics apply to all luminosity classes.

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